1. Field of Invention
This invention relates to barfeed apparatus for machine tools which allow barstock much longer than the spindle itself to be supported and guided.
This invention specifically relates to an apparatus and device to provide fluid to the space between the barstock and guide tube, for hydrodynamic support, of the type disposed within the guide tube.
2. Related Art
Hydraulic barfeed apparatus employing the hydrodynamic phenomena are commonly known. One such design is shown in U.S. Pat. No. 3,945,506 which describes a device that comprises a push piston with play in the guiding tube and a internal passage for the flow of oil to the barstock. As the needed flow around and through the push piston, for hydrodynamic support, is determined by the size and shape of the barstock being feed, and as the minimum pressure required to advance the barstock must be maintained on the push piston, to prevent the barstock bowing, using the pressure to control the flow works against the desired hydrodynamic support of the barstock. As fluid is constantly lost out the front of the barfeed apparatus, ineffectual flow results in insufficient or scanty filling of the guide tube, appreciable lessening the hydrodynamic support for the bars in the system. If a greater flow is needed to fill the area between the barstock and guide tube, for a smaller bar or bar shape, the internal passage must be increased, correspondingly for a larger bar or a shape of greater volume, requiring less flow, the internal passage must be decreased in order to maintain pressure on the push piston. The internal passage can be adjusted, however the adjustment is manual and requires the machine to be shut down and the push piston removed, causing loss in production. Improper adjustment results in increased, or loss, of pressure on the pusher, and little or no hydrodynamic support, increasing vibration and noise thus limiting the speed of the spindle and reducing productivity.
In yet another prior art design as described in U.S. Pat. No. 4,507,992, a push piston and a distribution system to supply oil to the push piston and between the barstock and guide tube to form an oil cushion is shown. The flow of oil delivered by the system can only be adjusted manually and a blockage in one or more of the distribution points could easily go undetected. Air trapped between distribution points, blockages at distribution points, and maladjustment can result in insufficient fluid in the guide tubes and excess, or low pressure on the barstock, appreciable lessening the hydrodynamic support. The resulting loss of support increases vibration and noise, limiting the speed of the spindle, reducing productivity.